The present invention relates to a starter arrangement for a helicopter driven by means of a reciprocating piston internal combustion engine in which at least one override clutch is arranged in a drive connection between the internal combustion engine and the rotor drive which separates the drive connection as soon as the output rotational speed of the override clutch, identical with the rotor driving rotational speed is higher than the input rotational speed thereof which is identical with the internal combustion engine rotational speed or with the transmission output rotational speed of a transmission connected ahead of the override clutch.
Small helicopters are frequently driven by reciprocating piston internal combustion engines: a tensionable belt serves as drive connection between the internal combustion engine and the rotor drive. For starting the helicopter, at first the internal combustion engine is started with an non-tensioned belt and with a running internal combustion engine the rotor drive is accelerated by a slow, increasing tensioning of the belt for such length of time until the belt operates without slippage.
A direct drive connection between the internal combustion engine and the rotor is not possible as a rule during the start of the helicopter because reciprocating piston internal combustion engines at rotational speeds below the idling rotational speed generally have an insufficient smooth running, i.e., exhibit excessive torque fluctuations and the inert but sensitive rotor drive can therefore possibly be excited to non-permisssively high rotational vibrations, respectively, can be damaged thereby.
The tensioning of the belt during the start, however, requires a not-inconsiderable force application and a certain fine feel during the operation as otherwise undesirable vibrations can easily build up. Furthermore, the belt drive is subjected to a strong wear.
It is therefore the object of the present invention to provide a starting arrangement for a helicopter equipped with a reciprocating piston internal combustion engine which shortens the operation of the start and is constructed in a simple and reliable manner.
The underlying problems are solved according to the present invention in that the rotor drive and the internal combustion engine are provided with separate first and second electric motor starter devices and in a first phase of a starting operation initially the rotor drive is accelerated by means of the first starter device to a synchronous rotational speed and upon reaching the synchronous rotational speed in a following second phase, the internal combustion engine is started by means of the second starter device whereby the internal combustion engine takes over the drive of the rotor or rotors as soon as its rotational speed exceeds a value at which the override clutch establishes the power flow between the internal combustion engine and the rotor drive.
The advantages of the present invention reside in the first instance in the accelerated, more simple and more reliable starting operation of a helicopter. The arrangement necessary therefor is characterized by the simplicity of the utilized components as well as by robustness and far-reaching freedom of wear.